"Some of the worst vandalbots create accounts.
Still, your point is absolutely valid in the broader sense. What changes could be make that might allow us to mitigate the problems of anonymous proxies in a gentler way than wholesale blocking?
Keep in mind that ideas are essentially useless, at least as compared to simple running code. So those of us who want to get something done in this area have a responsibility to either code it, or make sure that our great heroes the programmers understand that their humble subjects would be overjoyed to see something good in this area. :-)"
http://lists.wikimedia.org/pipermail/wikien-l/2005-October/031398.html
It has been coded. The patch has been submitted. Now accept it. If not for Wikipedia, at least for other wikis running mediawiki.